Having just outlined her grand vision for taking the stress out of life in the capital, Oona King checks her mobile phone for messages. It contains the news that she has been anxiously waiting for: confirmation that she has been shortlisted to fight Ken Livingstone for the right to be Labour's candidate for London mayor in 2012.
Five years ago Ms King's political career was in ruins after she was ousted from her parliamentary seat following an acrimonious, intensely personal battle with George Galloway. Devastated by the defeat, she all but disappeared from public view. She seemed destined to be written off as a colourful footnote to the New Labour years – the high-flying, publicity-courting "Blair babe" brought down in her largely Muslim constituency by her support for the Iraq war.
Were she to clinch the Labour nomination and go on to beat Boris Johnson she would be the country's most senior elected female politician. Not to mention, its most senior black politician. It would rank alongside Lord Mandelson's return to Gordon Brown's side 18 months ago as the most remarkable political resurrection for years. But we are getting ahead of ourselves. First Ms King, who has effectively taken five years out of public life, has to overcome London's two best-known politicians to seize the Mayoralty. Can she stop Mr Livingstone, whose desire to run City Hall is undimmed despite his defeat by Mr Johnson?
She has an impressive roster of influential supporters, including Neil and Glenys Kinnock, former cabinet ministers Alan Johnson and Ben Bradshaw and 12 of the capital's Labour MPs. She remains close to the Miliband brothers, with whom she was at school, although will not be drawn on which one she will back for the Labour leadership.
Despite his eight years running London, Mr Livingstone will bizarrely be cast in the role of the anti-establishment candidate in the contest for the nomination. The left-right battles that tore Labour apart in the 1980s still reverberate.
Ms King's strategy for defeating him will be to portray herself as a break with the past, a generational change from the man immersed in the capital's politics since the 1960s. The Livingstone team is already accusing her of negative campaigning by trying to turn his age (64) into an issue. Ms King, 42, responds scornfully: "If there is one group being discriminated against in politics, it's not really older men, is it? Ken did things well when he was running the Greater London Council. I was a teenager then, I was 13 or 14 years old. I'm in my 40s now. He has been doing it for four decades. It's not about saying Ken is too old. I don't think anyone is too old really. It's about the policies they bring, the ideas they bring. It's whether someone has had their time."
The key to Mr Livingstone's defeat in 2008 was the vast vote for his Tory rival in four largely middle-class outer London boroughs, sparking recriminations in Labour circles that he had focused his efforts too narrowly on the party's inner-city strongholds.
Although Ms King's politics are rooted in the East End, where she lives in a converted pub, she says her youth and promise of change can appeal to the city's blue fringes; that she can offer the "inspirational leadership that can reach across traditional political boundaries" and win over enough Tory-leaning voters to topple Mr Johnson.
Ms King was only the second black woman MP after Diane Abbott. Once in the Commons, aged 29, she was destined for attention. Her looks attracted tabloid headlines, her cosmopolitan background endlessly examined (her father is an American academic who left the country over the Vietnam war, her aunt is the television presenter and agony aunt Miriam Stoppard). She had a gift for racy soundbites, spoke of her love of house music and swapped banter on Have I Got News For You.
But her time in Westminster came to a calamitous end in 2005 when Mr Galloway, riding a wave of fierce local opposition to the Iraq war, won the constituency for the Respect coalition. She later claimed that anti-semitism (her mother is Jewish) had cost her the seat.
Since being cast out by the voters, she has mixed work in the media – she is on sabbatical from her post as head of diversity at Channel 4 – with a spell in the Downing Street policy unit. Her diaries from her days as an MP painted the bleakest of pictures of life in Westminster as she struggled 16 hours a day to cope with the demands of an inner-city constituency. The pressure was so intense, she admitted, that her marriage to her Italian husband, Tiberio, was pushed to breaking-point, forcing the couple to seek counselling.
In addition they went through the anguish of five failed rounds of IVF before deciding to adopt – they have two children: Elia, five, and Kaia, three. Ms King maintains that her experience of motherhood, and her time away from the "Westminster bubble", has made her a better politician. She insists on an hour a day of "quality time" with her youngsters – "not just trying to get their eyes shut and teeth brushed".
She says: "I'm very conscious that every hour I take out with them during the campaign is an hour I'm not ringing people or shaking a Labour Party member's hand. "It jeopardises my chances, but you have to decide whether you want to jeopardise your kids' lives – and there's a limit. I hope Labour members will understand that and recognise the benefits you get from someone who actually knows the demands of being a real-life parent, a hands-on parent."
Thirteen years on from arriving on the political stage, Ms King is far from the care-free, slightly risqué character that she once cut in the Commons. Sipping Diet Coke on the balcony of a community centre in Westminster, she is vague about how long she has been seriously contemplating a tilt at the "very best job in the world". "The first time I was asked to run for Mayor was in 1999 when I was a fairly new MP and it wasn't the right time for me ... I've always had people contacting me about it and I'd always told them: 'I will think about it, but I'm not thinking about it at this moment'."
She has rapidly assembled a campaign team, operating out of offices in Canary Wharf, and secured financial backing for her run at the mayoralty. Ms King boils down her platform to three key aims – making London fairer, less stressful and more "liveable". She proposes giving the mayor new responsibility for driving up schools standards, guaranteeing paid work experience for school-leavers and refurbishing pensioners' homes in return for a small stake in their property's equity. She also wants to limit the mayor to two terms in office.
Other ambitions for increasing investment or boosting council house building in the city would, however, depend on persuading a Tory Chancellor overseeing savage spending cuts to loosen the purse strings.
She argues that her experience of "pushing and pulling the levers of power" during her time bargaining with, and on behalf of, Tony Blair means she could succeed in levering money out of the Government. "Negotiation with the prime minister of the day is a key responsibility of the mayor, so that experience stands me in very good stead."
Would she really be better at that than Mr Livingstone with his decades of experience? "Without a shadow of doubt... I think I would probably even manage to do a better job with Cameron than Boris Johnson has."
In their early outings in hustings and television studios, Ms King and Mr Livingstone have managed to strike a joshing, outwardly friendly tone, but there is a real edge to the contest – not least because her campaign manager, Jim Fitzpatrick, the MP for Poplar and Limehouse, is a Livingstone foe.
Ms King goes so far as to suggest that a Livingstone candidacy would hand victory to Boris Johnson in 2012. "For us to think we can win the election by having the same candidate at the same election with the same policy platform would be to gift the election to the Tories. We just can't afford that."
She says she is not asking for support from the party's "selectorate" because of her gender or ethnicity, but also says it cannot be ignored. "Labour members understand there is an equality issue here. We know it's virtually certain there will be a male leader of the party, so if they think the two candidates for Mayor are equally qualified, I hope they will look at giving an under-represented group the opportunity. For Labour to stay vital it needs to show that it can reflect contemporary Britain."